Portable oscillating fans are well known and commonly used to circulate air. Examples of oscillating fans include those found in U.S. Pat. Nos. 2,341,220; 2,725,184 and 2,811,304. These fans generally include a rotatable fan unit supported by a base such as a stand or a pedestal and which is arrange to oscillate about a vertical axis so as to enhance the circulation of air. In order to further enhance the air circulation capabilities of the fan, the fan unit may be further mounted for limited tilting movement both backward and forward about a horizontal axis. Such tilting of the fan unit permits the fan to more efficiently direct air circulation in a plurality of directions.
While it may be desirable provide a wide range of positions through the fan unit may be tilted, certain positions may result in the fan being unstable when supported on a horizontal surface such as a table. Applicable regulatory standards which mandate the degree of stability that a fan must maintain, such as those promulgated by Underwriters Laboratories (UL), effectively place limits on the degree to which a fan unit may be tilted with respect to the base especially in the rearward direction. These limitations on fan unit tilt, prevent inadvertent toppling of the fan when it is supported on a sloped surface such as a damaged table. UL requirements therefore dictate that the fan be operable in all modes (oscillating, non-oscillating, tilted, etc.) when supported on a 10.degree. sloped surface. Thus, oscillating fans are currently designed so that the fan unit is restricted, to some degree, from being tilted to a position which would cause the fan to easily topple over due to its unbalanced center of gravity and thereby fail the 10.degree. stability test.
Notwithstanding the need to limit the amount of horizontal tilt of a table supported fan unit during use, it may become necessary to tilt the fan unit with respect to the base beyond the dictated limits. In one such situation, convenient and economical packaging of the fan for transportation and sale is provided by permitting the fan unit to be collapsed forward towards the base into a smaller configuration. Such collapsing of the fan is achieved by tilting or rotating the fan unit horizontally with respect to the base beyond the typical set limits. While allowing such collapsing movement of the fan unit with respect to the base, assurances must be provided that during use the fan unit cannot be easily tilted beyond the code dictated limits. Commonly assigned U.S. Pat. No. 4,732,539 addresses this concern by providing a fan having a fan unit which may be collapsed with respect to the base for convenient packaging yet limits the amount of fan unit tilt with respect to the base during use.
In another situation, certain oscillating fans are designed for dual positioning, i.e., the fan may be supported on a horizontal surface such as a floor or table or may be mounted to a vertical surface such as a wall. In this situation, the fan unit must be moveable through a wide range of positions with respect to the base to allow for both table supported and wall mounted positioning of the fan. As a table fan, the fan unit may be generally vertically aligned with the base and when used as a wall mounted fan, the fan unit may be rotated or tilted 90.degree. or more with respect to the base. As may be appreciated, a fan which would permit such a wide degree of fan unit tilt would not pass the applicable 10.degree. stability test of UL if the fan is inadvertently supported on a sloped table in its wall mounted configuration. Fans which permit such wide range of fan unit tilt need to include a locking mechanism which will limit the amount of fan unit tilt in a table configuration to only those positions which provide stability and therefore pass the 10.degree. stability test. Such a locking mechanism may be overcome by deliberate action of the user to allow movement of the fan unit to a wall mounted position. Thus the fan could not be inadvertently positioned in an unstable position during table supported use.
It is therefore desirable to provide an oscillating fan which allows movement of a fan unit with respect to the base through a wide range of angles so as to permit the fan to be used in either a table supported or wall mounted configuration and yet permit the range of motion to be restricted in a table supported configuration so as to meet applicable code regulations.